Age resisters and stabilized rubber compositions containing same



United States Patent AGE RESISTERS AND STABHIZED RUBBER COMPOSITIONSCONTAINING SAME Kurt Ley, Helmut Walz, and Wolfgang Redetzky,Leverlrusen, and Helmut Freytag, Cologne-Stammheim, Germany, assignorsto Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, acorporation of Germany No Drawing. Filed May 18, 1966, Ser. No. 550,899Claims priority, application Germany, Mar. 28, 1962,

8 Claims. (Cl. 26045.8)

This invention relates to novel compounds, their production and theiruse as age resisters in natural rubber and synthetic rubber-likepolymers, and is a continuationin-pait of SN. 267,930, filed Mar. 26,1963, and SN. 398,421, filed Sept. 22, 1964, both of which are nowabandoned.

It is known that substituted phenols such as 2,6-ditertiarybutyl-4-methylphenol or diphenols such as 2,2-methylene-di-(4-methyl-6-tertiary butyl-phenol) may be used as ageresisters for pale and colored rubber articles which should not becomediscolored or only to a slight extent in daylight. The compounds soprepared have the disadvantage that they have either an inadequateprotective eiiect or are not satisfactory in preventing discoloration onexposure to natural light and are to a certain extent not readilyavailable commercially. Furthermore, 2,5-alkylated hydroquinones impartonly a very slight protection to rubber against oxidation.

It has now been found that compounds of the general formula (Formula I):

wherein each of R R and R is hydrogen, an alkyl radical or a cycloalkylradical, and wherein R and R can be bonded directly to each other, andwherein R and R together with the carbon atom to which they are attachedcan represent a 6-membered carbocyclic ring, which can optionally besubstituted by alkyl radicals, and wherein R represents hydrogen or oneor two alkyl radicals or an optionally substituted phenyl radical andwherein R and R represent alkyl or cycloalkyl radicals, and wherein Rand R can also be bonded directly to one another, through a carbon orhetero atom bridge, can be used as age resisters for natural andsynthetic rubber. The alkyl radicals advantageously represent loweralkyl radicals, which can contain up to 6 carbon atoms.

If R represents a phenyl radical then it can contain, for example, assubstituents, alkyl radicals, preferably lower alkyl radicals such asmethyl or ethyl, or alkoxy groups such as methoxy or ethoxy.

The compounds used according to the invention may be obtained by addingon enamines to p-benzoquinones with free 2,3-positions.

The enamines used for the reaction correspond for example to thefollowing general formula (Formula II):

in which the radicals R to R have the meaning indicated above in FormulaI. Examples of such compounds 3,344,109 Patented Sept. 26, 1967 areisobutenylpyrrolidine, -piperidine, -morpholine, -diethylamine,-dimethylamine or the corresponding cyclohexenyl compounds. The alkylradicals are preferably lower alkyl radicals containing up to 6 C-atoms.Specific enamines include N-(isobutenyl) morpholine,

N-(isobutenyl) piperidine,

N- a-methylenecyclohex-F: -enyl morpholine,N-(a-methylene-cyclohexyl)morpholine or N-(a-methylenemethylcyclohex3-enyl)morpholine.

Apart from p-benzoquinone itself, quinones which are substituted in the5- and/or 6-position, e.g. by lower alkyl radicals such as methyl orethyl radicals may also be used for the reaction. Examples of thep-quinones are the following compounds:

The production of the compounds used according to the invention isadvantageously carried out in an inertsolvent, such as benzene, toluene,methanol, ethanol or benzine. The quinone is generally providedinitially and the enamine is introduced in small charges at temperaturesbetween 0 and C., advantageously at room temperature. It may beexpedient for the reaction mixture thereafter to be heated for some timeto its boiling point.

The di-hydroxycyclobutanes separate out on cooling. The compounds usedaccording to the invention are suitable as age resisters both fornatural rubber and for synthetic rubber such as butadiene-styrenecopolymers and butadiene-acrylonitrile copolymers. The compounds may beused both for protecting crude rubbers and mixtures thereof and thevulcanizates. In each case, between 0.1 and 5% by weight, preferablybetween 0.25 and 2% by weight calculated on the elastomers is added inthe usual manner, e.g. by m'ming on a roller or on an internal mixer.

Oxidation processes which lead to softening (degradation) or hardening(cyclization), depending on the type of elastomer used, are effectivelyprevented or greatly retarded by these additives, and no discolorationsoccur on exposure to light such as is characteristic for the ageresisters of the secondary aromatic amine type (e.-g.phenyl-fl-naphthylamine) which have been used for a long time.

EXAMPLE 1 The following mixture was prepared on a roller:

Parts by weight Age resister as given in Table l.

The substance is then vulcanized in a pres-s for 17 minutes at 2atmospheres above atmospheric pressure (133 C.). The vulcanizate soobtained has the following mechanical properties:

Table 1 (a) With 1% by weight of2,2'-methylene'-'di-(4-methyl-o-tertiary bntyl-phenol) (for comparison)Color of the vulcanizates:

Before illumination White. After 2 months weathering in the open Palepink.

air Formation of elephant skin: After 2 months weathering in the openair None.

(b) With 1% by Weight of 2,6-di-tertiary butyl-4- methylphenol (foroomparison) Load at Elas- Shore Strength, Elon- 450% ticity, herdkgJem.gation, elongation, 20 C./ ness percent kg/cm. 75 0., A

percent Before aging 190 670 09 70/74 48 Aging in an oxygen bomb(according to BierenD avis) 21 atmospheres above atmospheric pressugecofoxygen at After 6 days 135 555 83 66/73 49 After 11 (lays. 120 585 6357/67 45 After 16 days 75 560 47 46/54 42 Color of the vulcanizates:

Before illumination White. After 2 months weathering in the open air Do.Formation of elephant skin: After 2 months Weathering in the open airNone. (c) With 1% by weight of compound O-GH-N (ll-CH OH;

I OH

Load at Elas- Shore Strength, Elon- 450% ticity, hardkg/crnfi gation,elongation, 20 C./ ness percent kg./cm. 75 0., A

percent Before aging 225 700 68 70/72 49 Aging in an oxygen bomb(according to Bierer-Davis) 21 at mospheres above atmospherie pressureof oxygen at 70 0.:

185 590 94 67/72 52 145 540 91 63/70 50 After 16 days 145 545 90 50/6459 Color of the vulcanizates:

Before illumination White. After 2 months weathering in the open air Do.Formation of elephant skin: After 2 months weathering in the open airNone.

(d) With 1% by weight of the compound O-GH-N I (Z-43H; 5 CH;

Load at Elas- Shore Strength, Elon- 450% ticity, hardlrgJcm. gation,elongation, 20 0.] ness percent kgJcm. 75 0., A

percent Before aging 230 680 73 73/78 50 Aging in an oxygen bomb(according to Bierer-Davis) 21 atmospheres above at mospherie pressureof oxygen at 70 0.:

After 6 dnys 1. 175 555 100 67/73 53 After 11 days- 160 545 88 63/68 52After 16 days 140 515 97 59/67 50 5 Color of the vulcaniza-tes:

Before illumination White. After 2 months weathering in the open airPale cream color. Formation of elephant skin: After 2 months weatheringin the open air- None.

(e) With 1% by weight of the compound OCHN ' l L (|1-CH CH3 I OH Load atEias- Shore Strength, Elon- 450% ticity, hardkg./om. gation, elongation,20 C./ ness percent lag/cm. 75 0., A

percent Beforeaging 185 615 82 74/78 51 Aging 111 an oxygen bomb(according to Bierer-Davis) 21 atmospheres above atmospheric pressure ofoxygen at 70 C: After 6 days 105 53 After 11 days 95 52 After 16 days S052 Color of vulcanizates:

Before illumination After 2 months weathering in the open air monthsweathering in the open air..

White.

None.

Cream colored.

(f) With 1% by weight of the compound Load at Elas- Shore Strength,Elon- 450% ticity, hardkgJom. gation, elongation, 20 O./ ness 7 percentkgJom. 75 0., A

| percent N O Y Before ing 195 665 72 68/74 50 I Aging in an oxygen I Ibomb (according to C (3112 Bierer-Davis) 21 atmospheres above at- H Cmospheric pressure I of oxygen at 70 0.: 5 Hz After6days 180 595 8965/68 52 After 11 (lays A 150 570 35 63/68 50 on After 16 days 135 55082 54/65 47 1 Load at I E1as Show Color of the vulcanizates: Strength,Elon- 450% tigity, hard- Before exposure to light White. kg/cm} fifigg5g, 8 2 After weathering in the open for 2 ercent months Do.

Elephant skin formation: After weathering in Before aging .1 225 675 7371/74 50 20 the open for 2 months None. Aging in an oxygen bomb(accordlngto (1) Wlth 1% by we1ght of the compound Bierer-lgavis) g1atmosp eresft ove m atmospheric pres- OC H-N O sugecol oxygen at I IAfter fidays .2 155 550 96 65/70 52 0 After 11 days 120 525 33 55/62 48After 16 days 85 445 80 46/53 48 H Color of the vulcanizates: (53

Before illumination White. After 2 months weathering Lo (1 E1 1n theopen air Slightly cream colored. Strength Etonf g; 32%? Formation ofelephant skin: After gJOmJ gzt gm 2 5 5 3g: 8/ 1125s 2 months weatheringin the p m n percel'lt open air None.

W 1117 b ht fth d fieioreaging 205 685 68 67/74 50 0 1t Wei 0 e com oung In an y n 0 y g p bomb (according to Bierer-Davis) 21 0CH-N N-CH-Oatmospheres above I 40 atmospheric pressure of oxygen at CCH3 HaC-C- 700.:

Afterti days 175 590 86 64/68 51 CH H O After 11 days 135 550 84 60/6350 After 16 days 120 530 82 53/69 48 I I 0H 0H Color of the vulcamzates:

Before exposure to light White. Load at E1 Show After weathering in theopen for 2 Strength, Elon- 450% ffgity, herdmonths Do.

2 5 5232 11; 3252 2 9? 2 85} 11355 Elephant skm formation: Afterweathering in the open for 2 months None.

Before agim 210 695 49 66 48 (j) With 1% by weight of the compound Agingin an 1 n bomb (according to 0. CH N Z) Bierer-Davis) 21 atmospheresabove at- I mospheric pressure C of oxygen at 70 0.:

After 6 days 175 615 80 64 52 After 11 days 135 585 74 49 After 16 days125 575 68 52 47 OH I Color of the vulcanizate: 60 CH7 7 Beforeillumination White. After 2 months weathering in the open Load at Shorei DQ Sktrengtlg, Etlion- 1 450% tif igy, hard- .cm. v 2O Formation ofelephant skin: After 2 months g/ a 22723? 5 f Z weathering in the open8.11 None. 7 percent (h) With 1% by weight of the compound Befo eaging215 695 67 68/75 56 Aging in an oxygen bomb (according to OCHN OBierer-Davis) 21 I I 70 atmospheres above atmospheric pres- -0 sure ofoxygen at After 6 days 180 595 88 63/67 52 After 11 days 135 550 57/6550 After 16 days 540 79 56/62 48 7 8 Color of the vuloanizates:

Before exposure to light White. St m E1 7 31 1 3 1 reng on- 45 icity arAfter Weathermg m the Open for 2 kgJcmJ gation, elongation, 20 0.7 nessmonqls 130- percent kgJom. 75 0., A Elephant skin formation: Afterweathering in Percent the open for 2 months None.

Before aging 215 700 68 68/70 49 (It) With 1% by weight of the compoundAglng 1n the oxygen bomb (according to Bierer-Davis) 21 at- N-H C-Omospheres above at- I 10 mospherlc pressure at oxygen at 70 0.: aC-C CH;After 6 days 155 580 88 62/65 61 After 11 days 125 560 74 58/60 41 11:0After 16 days 80 510 65 50/54 43 OH Color of the vulcanizates:

Before exposure to light White. Load at may share After weathering inthe open for 2 Strength, Elon- 450% tlzgity, hardmonths Do. kg/cm 32522Eg g f Elephant skin formation: After weathering in percen tl 20 theopen for 2 months None. Before aging 220 700 66 68/71 49 W 1% by g t ofthe mpo nd Aggng ki)n(the nigger;

om 3600! mg 0 Btierer-lgavis) i1 0 N HC 0 8 HIOSD GIGS a 0V8 atmosphericpres- I sure 0 oxygen at 70C.: H 0 After 6 days 150 570 83 62/66 50 BBCAfter 11 days 135 670 75 59/61 48 After 16 days 115 550 73 56/59 45 30OH Color of the vulcamzates:

Before exposure to light White. After weathering 1n the open for 2 Loadat E1 Show months Do, Strength, Elon- 450% n w, hard- Elephant slrinformation: After weathering in $2 0 5; 1225233 32 i the open for 2months None. p c

(1) With 1% by weight of the compound Before aging v 215 705 65 67/72 50Aging in an oxygen 0 N HCO bomb (according to 40 Bierer-Dzwis) 21atmospheres above at- H C- mospheric pressure of oxygen at 70 0.: 11,After 6 days 165 580 90 63/68 51 mm 11 days i. 140 580 so 61/65 43 After16 days 115 545 78 tit/63 47 Color of the vulcanizates: Before ex osureto e p Loadat Elas- Shore hght T stren tl Elon- 450% tit ity, hard-Elephant skin formation: After weathering 1n 325333? 22. if the open for2 months None.

percent 50 (o) Wlth 1% by weight of the compound Before aging 220 705 6766/68 49 m Aging in an oxygen bomb (according to O N-HC--O Bierer-Davis)21 at- I mospheres above atmospheric pressur HsC-C of oxygen at 70 0.:

After 6 days 170 595 35 /70 50 H30 After 11 days 135 570 78 61/65 45 0CH1 After 16 days 110 535 78 53/62 46 6 011 Color of the vulcamzates: 0Before exposure to light White. After weathering in the open for 2 Loadat Elw Show months Do. i po 911- 1 450% tigity, hard- Elephant skinformation: After weathering in 65 @2 55; 2253 33 3g. 3

the open for 2 months None. percent W1th 1% y welght of e compoundgegoreggmg 205 690 76 69,72 50 g 11g 811 oxygen bomb (accordmg to O N HCBierer-Davis) 21 7 atmospheres above H8O 0 O1 atmospheric pressure ofoxygen at Bag 0.:

After-6 days 155 580 83 62/67 50 Atter 11 days 140 570 30 59/62 48 After16 days 105 525 55/61 46 OH 9 Color of the vulcanizates:

Before exposure to light White.

After weathering in the open for 2 months Do. Elephant skin formation:After weathering in the open for 2 months None.

EXAMPLE 1(b) With 1% by weight of the compound I o on m Load at Elas-Shore Strength, Elon- 450% ticity, hardkgJcm. gation, elongation, 20 0.]ness percent kgJem. 75 0., A

percent Prior to the aging 225 680 78 70/73 52 Aging in the oxygen bomb(according to Bierer-Davis) 21 atmospheres above atmospheric pressure ofoxygen at 70 0.:

After 6 days 185 580 93 70/ 68 52 After 11 days- 145 540 90 60/67 51After 16 days 140 545 83 57/63 49 Color of the vulcanizates:

Before exposure to light White.

After 2 months weathering in the open air Do. Formation of elephantskin: After weathering in the open for 2 months None.

EXAMPLE 2 The following mixture is prepared on a roller:

Parts by weight Age resister as shown in Table 2.

The mixture is vulcanized in a press for 30 minutes at 4 atmospheresabove atmospheric pressure (151 C.). The vulcanizate so obtained has thefollowing mechanical properties:

Table 2 (a) With 2.5% by weight 2,2-methylene-di-(4-methy1- 6-tertiarybutyl-phenol) (for comparison) Load at Elas- Shore Strength, Elon- 200%ticity, hardkg./cm. gation, elongation, 20 C./ ness percent kgJcm. 750., A

percent Before aging 60 875 11 38/43 50 Aging in a heating cupboard(according to Geer) at 100 0.:

After days 50 380 29 44/55 65 After days 55 305 42 40/56 71 After 15days 65 210 62 38/45 73 10 Y (b) With 2.5% by weight of 2,6-di-tertiarybutyl-4- methylphenol (for comparison) Load at Elas- Shore .Strength,Elon- 200% ticity, hardkgJcrn. gation, elongation, 20C] ness percentkg./cm. 0., A

percent Before aging 60 970 10 39/41 49 Aging in a heating cupboard(according to Geer) at 100 0.:

After 5 days 40 280 31 47/56 64 After 10 dayS 45 230 42 39/55 73 After15 days 50 160 37/54 76 (0) With 2.5 by Weight of the compound 00HN 0 Il (ll-CH3 CH;

I OH

Load at Elas- Shore Strength, Elon- 200% ticity, hardkgjcm. gation,elongation, 20 0./ ness percent kg./cm. 75 0., A

percent Before aging 60 685 14 39/46 66 Aging in a heating cupboard(according to Gear) at 100 0.:

After 5 days 50 390 28 45/55 63 After 10 days 55 355 38 41/57 72 After15 days 60 260 48 38/55 75 (d) With 2.5 by weight of the compound(l)-(]HN NOHO (ll-0H H;C-0 CH; HaC

Load at Elas- Shore Strength, Elon- 200% ticity, hardkgJeni. gation,elongation, 20 C./ ness percent kg./cr.n. 75 0., A

percent Before aging 80 770 14 40/45 56 Aging in a heating cupboard(according to Geer) at 0.:

After 5 days 55 425 29 43/54 66 After 10 days 55 335 40 39/55 72 After15 days 55 245 52 38/55 75 EXAMPLE 3 The following mixture is preparedon a roller:

Parts by weight Styrene-butadrene rubber 100.0 Zinc oxide 5.0 Carbonblack 45.0 Stearic acid 1.7 Aromatic mineral oil plasticizer 7.0Tetramethylthiuramdisulfide 3.0 Z-mercaptobenzthiazole 1.0

7 Age resister as indicated in Table 3.

The mixture is vulcanized for 20 minutes at 4 atm. (151 C.) in thepress. The 'vulcanizate obtained has the following mechanical values:

Table 3 (a) With 2.5% by weight of 2,2'-methylene-bis-(4- methyl-6-tert.butyl-phenol) (for comparison) Load at Elonga- 200% Hard- Elas-Strength, tion at elonganess ticity,

lrgJcm. break, tion, (Shore percent percent kgJcm. A)

Prior to the aging- 175 820 26 55 48 Aging in hot air gGeer test) at 125Enter 4 days 160 350 s1 s2 43 After days 95 105 72 35 (b) With 2.5% byWeight of the compound O-CH-N b (O I OH Load at Eionga- 200% Hard- Elas-Strength, tion at elonganess ticity, kg./em. break, tion, (Shore percentpercent kgJcm. A)

Prior to the aging. 170 725 32 57 49 Aging in hot air (Gear test) at 125Liner 4 days. 170 445 62 62 44 After 10 (12-375.... 135 230 116 67 41EXAMPLE 4 The following mixture is prepared on a roller:

Parts by weight Acrylonitrile-butadiene rubber 100.0 Zinc oxide 10.0Carbon black 45.0 Stearic acid 1.0 Aromatic mineral oil plasticizer 1.0Tetramethylthiurarndisulfide 440 Age resister as indicated in Table 4.

The mixture is vulcanized for 35 minutes at 4 atm. (151 C.) in thepress. The vulcanizate obtained has the following mechanical values:

Table 4 (a) With 3% by weight of 2,2'-methylene-bis-(4-methyl-6-tert.butyl-phenol) (for comparison) The compounds used according to theinvention were obtained as follows:

(a) 0CHN 0 I OH 54 g. of p-benzoquinone are suspended in 400 m1. ofmethanol and 88 g. of N-(a-methyIenecycIQheX-S-enyl)- morpholine areadded dropwise thereto while stirring. The reaction mixture is therebyheated up to 60 C. After the solution has cooled to 50 C., 50 ml. of a20% aqueous sodium dithionite solution are added and the mixture isthereafter cooled to 10 C. The precipitated product is suction-filtered.There are obtained 90 g. of a compound which, after allowing to dissolveand crystallize from benzene-benzine, shows a melting point of 166- 167C.

C H O N (287)-molecular wt.:

Calculated: C, 71.3; H, 7.3; N, 4.87 Found: C, 71.3; H, 7.5; N, 5.10

54. g. of p-benzoquinone are reacted as in Example 5a with 91 g. ofN-(u-methylenecyclohexyl) -morpholine. There are obtained g. of acompound, which melts at temperatures from 164-165" C.

Calculated: C, 70.5; H, 7.98; N, 4.05 Found: C, 70.9; H, 8.00; N, 4.90

54 g. of p-benzoquinone are reacted as in Examples 5a and 5b with 97 g.of N-(a-methylenemethylcyc1ohex- 3-enyl)-morpholine. There are obtained80 g. of a compound which melts at temperatures from 186-189 C.

Calculated: C, 71.8; H, 7.65; N, 4.65 Found: C, 71.7; H, 7.80; N, 4.60

46 g. of 2-(a-phenyl)-p-benzoquinone are suspended in 150 ml. ofmethanol and thereafter 36 g. of iso butenylmorpholine are addeddrop'Wise While stirring. The reaction mixture is thereby heated to 60C. After the solution has been cooled to 50 C., 50 ml. of a 20% aqueousdithionite solution are added, the solution is cooled to 10 C. and theprecipitate is suction-filtered. After Washing with Water and thereafterdrying, the compound melts from 158160 C. 70 g. are obtained.

C20H23O3N1 Calculated: C, 74.0; H, 7.08; N, 4.30 Found: C, 73.5; H,7.10; N, 4.35

19.8 g. of 2-(o-tolyl)-p-benzoquinone are reacted with 14.1 g. ofisobutenylmorpholine, as in Example d, and worked up. There are obtained25 g. of a substance which melts from 178180 C.

Calculated: C, 74.3; H, 7.38; N, 4.13 Found: C, 73.9; H, 7.40; N, 4.30

44 g. of 2-(o-chlorophenyl)-p benzoquinone are reacted with 28.2 g. ofisobutenylmorpholine, as in Example 5d, and worked up. There areobtained 62 g. of a compound, which melts from 198200 C.

C20H2203N1C11 1 Calculated: C, 66.8; H, 6.13; N, 3.9 Found: C, 66.2; H,6.20; N, 4.1

40 g. of Z-(p-tolyl)-p-benzoquinone are reacted with 28.2 g. ofisobutenylmorpholine, as in Example 5d, and worked up. There areobtained 63 g. of a compound, which melts from 169171 C.

Calculated: C, 74.3; H, 7.38; N, 4.13 Found: C, 74.2; H, 7.40; N, 4.20

I H O OCH I OH

42.8 g. of 2-(p-anisyl)-p-benz0quinone are reacted With 28.2 g. ofisobutenylmorpholine, as in Example 5d, and Worked up. There areobtained 68 g. of a compound, which melts from 155157 C.

Calculated: C, 71.0; H, 7.2; N, 3.95 Found: C, 70.8; H, 7.2; N, 4.10

64.8 g. benzoquinone-( 1,4) are dissolved in 800 ml. of benzene. 83.4 g.of isobutenylpiperidine are added drop- Wise at 10 to 20 C. Whenaddition is completed, the mixture is stirred for another hour at roomtemperature. The precipitated product is removed by suction. g. areobtained. RediSSolVing several times from methanol gives almostcolorless crystals of melting point 162 to 163 C.

C15H21O2N Calculated: C, 72.8%; H, 8.5%; N, 5.65%; O

64.8 g. 'benzoquinone-( 1,4) are dissolved in 800 m1. of benzene. 84.6g. of isobutenylmorpholine are added drop- Wise at 10 to 20 C. withstirring. When addition is completed, the mixture is stirred for another/2 hour and the precipitate is removed by suction. 90 g. are obtained.Redissolving from methanol with the addition of a small amount ofaqueous dithionite solution produces crystals of melting point 186 to188 C.

C14H19O'3N Calculated: C, 67.30%; H, 7.65%; O, 19.25%; N,

Found: C, 67.0%; H, 7.7%; O, 19.7%; N, 5.6%

37.5 g. of p-benzoquinone are dissolved in 500 ml. of benzene. 32.4 g.of iso-butenylpyrrolidine are added drop- Wise. When the reaction hasdied down, the product is heated to boilin for hour and then cooled. Theprecipitated material is removed by suction. 45 g. of a compound meltingat to 144 C. are obtained.

Calculated: C, 72.2%; H, 8.15%; N, 6.00% Found: C, 71.6%; H, 8.04%; N,5.73%

32.4 g. of p-benzoquinone are dissolved in 500 ml. of benzene. 48 g. ofcyclohexenylpiper-idine are added dropwise. The mixture is then heatedto boiling for /2 hour. 60 g. of a compound which melts at 108 to 120 C.with evolution of gas crystallize out on cooling.

A corresponding compound is obtained when 50.1 g. ofcyclohexenylrnorpholine are used instead of cyclohexenylpiperidine.Melting point 99102 C. with evolution of gas.

Calculated: C, 78.8%; H, 8.25%; N, 4.0% Found: C, 78.5%; H, 8.20%; N,4.0%

55 g. of p-benzoquinone are dissolved in 300 ml. of methanol. 49 g. ofN,N-di-isobutenylpiperazine are added dropwise. The temperature of thereaction mixture rises. The precipitated compound is removed by suctionand washed with methanol. 90 g. of a product melting at 222 to 225 C.are obtained.

Calculated: C, 70.2%; H, 7.34%; N, 6.83% Found: C, 69.3%; H, 7.56%; N,7.20%

54 g. of p-benzoquinone are suspended in 600 ml. of methanol. 95 g. ofN-(u-methylen-endomethylencyclohex- 3-enyl)-morpholine are addeddropwise while stirring and intensively cooling in such a manner thatthe temperature of the mixture does not rise above 10 C. Thereafter themixture is stirred for another two hours at 10 C. and subsequentlyheated to boiling. Then the solution of 10 g. of sodium-dithionite in200 ml. of water are added. The reaction mixture is heated another twohours to boiling, subsequently cooled to 5 to C. and thereafter stirredfor another two hours at 5 to 10 C. The precipitate obtained is removedby suction and washed with a mixture of methanol and water in the ratioof 2 to 1. 117 g. of the compound the formula of which is given aboveare obtained. After re-crystallizing from methanol the product has amelting point of 209 C.

Calculated: C, 72.3%; H, 7.1%; N, 4.7% Found: C, 72.34%; H, 7.37%; N,4.68%

What'we claim is: 1. As a new composition of matter, natural rubber or asynthetic diene rubber which is stabilized against discoloration fromexposure to light by the incorporation therein of about 0.5-5% byweight, based on the rubber, of a compound of the formula wherein R ishydrogen, lower alkyl, phenyl, alkyl-phenyl, or alkoxy-phenyl; R and Rare hydrogen or lower alkyl, or are connected together to form acarbocyclic ring; and wherein R and R may be connected to each otherthrough polymethylene groups or through a heterocyclic ring containingan O atom or another N atom.

2. The composition of claim 1 wherein the R and R groups of saidcompound are connected together to form an unsaturated carbocyclic ring.

3. The composition of claim 1 wherein the R and R groups of saidcompound are connected together to form a six-membered unsaturatedcarbocyclic ring.

4. The composition of claim 1 wherein the R and R groups of saidcompound are connected together to form an unsaturated carbocyclic ringhaving only one unsaturated bond.

5. The composition of claim 1 wherein the R and R groups of saidcompound are connected together to form a carbocyclic ring which issubstituted by at least one methyl group.

6. The composition of claim 1 wherein the R and R substituents of saidcompound are connected together through an oxygen atom to form amorpholino ring.

7. The composition of claim 1 wherein said compound has the formula 8.The composition of claim 1 wherein said compound has the formulaReferences Cited UNITED STATES PATENTS 5/1942 Paul et al. 260-800 6/1943Paul 260-880 X DONALD E. CZAJA, Primary Examiner.

LEON I. BERCOVITZ, Examiner.

'15 WELSH, Assi tgmt Examiner.

1. AS A NEW COMPOSITION OF MATTER, NATURAL RUBBER OR A SYNTHETIC DIENERUBBER WHICH IS STABILIZED AGAINST DISCOLORATION FROM EXPOSURE TO LIGHTBY THE INCORPORATION THEREIN OF ABOUT 0-5-5% BY WEIGHT, BASED ON THERUBBER, OF A COMPOUND OF THE FORMULA